This summer's Olympics will increase the already "extreme" risk of a flu pandemic spreading in the UK, according to a new report.

Britain was ranked second only to Singapore for its vulnerability to the rapid spread of an influenza outbreak.

The UK is at such high risk because of its densely-packed cities, highly-mobile population and popularity as a global travel hub, Bath-based analysts Maplecroft found.

The study said the London Olympics in July and August will increase the danger of flu spreading because an extra 5.3m foreign tourists - many from countries where any pandemic is likely to emerge - are expected to visit Britain for the Games.

Maplecroft's influenza pandemic risk index rates five countries at "extreme" risk for the spread of the disease, with Singapore top, followed by the UK, South Korea, the Netherlands and Germany.

But Britain was also judged to be one of the 10 countries best placed to withstand any outbreak thanks to its strong governance, effective health infrastructure and good communications networks.

The report found that South-East Asia was most likely to see a new flu pandemic emerge, with the region containing six of the 10 countries at highest risk.

Four nations were considered "extreme" risk in this category, with Cambodia top, followed by Bangladesh, China and Vietnam.

The authors expressed particular concern about China, whose growing prosperity has led to higher consumption of meat and therefore a rise in livestock numbers.

They noted: "The likelihood that influenza strains will emerge within China takes on extra significance in light of the fact that the country is also highly vulnerable to the spread of disease (it ranks 18th and high risk in Maplecroft's risk of spread index), which increases the risk of a pandemic outbreak."

Past flu pandemics have caused disaster on a global scale. The 1918 Spanish Flu outbreak killed up to 40 million people, more than the number who died in the First World War.

The H1N1 swine flu outbreak in 2009-10 claimed 457 lives in the UK. Experts believe more severe pandemics may occur in the future, possibly as a result of a mutated bird flu strain.